Hypothesis: Zirconia microparticles produced by sol–gel synthesis have great potential for photonicapplications. To this end, identifying synthetic methods that yield reproducible control over size uniformityis important. Phase transformations during thermal cycling can disintegrate the particles. Therefore,understanding the parameters driving these transformations is essential for enabling high-temperatureapplications. Particle morphology is expected to influence particle processability and stability. Yttriadopingshould improve the thermal stability of the particles, as it does in bulk zirconia.Experiments: Zirconia and YSZ particles were synthesized by improved sol–gel approaches using fattyacid stabilizers. The particles were heated to 1500 C, and structural and morphological changes weremonitored by SEM, ex situ XRD and high-energy in situ XRD.Findings: Zirconia particles (0.4–4.3 lm in diameter, 5–10% standard deviation) synthesized according tothe modified sol–gel approaches yielded significantly improved monodispersities. As-synthesized amorphousparticles transformed to the tetragonal phase at 450 C with a volume decrease of up to 75%and then to monoclinic after heating from 650 to 850 C. Submicron particles disintegrated at850 C and microparticles at 1200 C due to grain growth. In situ XRD revealed that the transition fromthe amorphous to tetragonal phase was accompanied by relief in microstrain and the transition fromtetragonal to monoclinic was correlated with the tetragonal grain size. Early crystallization and smallerinitial grain sizes, which depend on the precursors used for particle synthesis, coincided with higher stability.Yttria-doping reduced grain growth, stabilized the tetragonal phase, and significantly improved thethermal stability of the particles.

Journal of colloid and interface science 448, 582 - 592 (2015). doi:10.1016/j.jcis.2015.02.049

Published by Elsevier, Amsterdam [u.a.]